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• help with matlab and Discrete Fourier transform

  - by user504363

  Hi all I have previous experience with Matlab, but the problem that I face some problems in apply a problem in (DSP : Digital signal processing) which is not my study field, but I must finish that problems in days to complete my project. all i want is help me with method and steps of solving this problem in matlab and then I can write the code with myself. the problem is about the signal x(t) = exp(-a*t); 1) what's the Discrete Fourier transform of the sampled signal with sample rate fs 2) if a=1 and fs =1 , plot the amplitude spectrum of sampled signal 3) fix the sampling frequency at fs = 1(hz) [what's it mean ?] and plot the magnitude of the Fourier Transform of the sampled signal at various values of a thanks

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• c# wrapper for a c DLL

  - by Without me Its just Aweso

  I'm attempting to write a wrapper so that my C# application can use a DLL written in C. Here is a method defintion that i'm trying to wrap: void methodA(const uint32_t *data); //c header declaration The issue I'm having is trying to figure out how to give a equivalent pointer from c#. In c# I want it to operate on a: UInt32 data[] //my c# object i want to be able to pass in but how do I give an equivalent pointer in my wrapper? I have tried ref data //my attempt at giving an equivalent pointer to the DLL but that doesnt seem to be working. Using debug statements in the DLL I can see that the values it gets that way are not what I'm attempting to pass in. So my question boils down to have do I properly wrap a c fuction that is using a pointer to reference an array?

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• SOCKET chat C# with private messaging

  - by Sergei

  I want to create SOCKET chat(server + clients) with private messaging. When client write smth to stream, he should notify server that it is private message for user X, how can i do this? Actually i can do smth like this: string command = "PRIV|" + txtMessage.Text; swSender.WriteLine(command); but i think it isn't good, for example if user wants send message like our "PRIV|" flag it will be errors public class TestChat { private StreamWriter swSender; private IPAddress ipAddr; private void InitializeandSend() { //ip from text box ipAddr = IPAddress.Parse(txtIp.Text); // Start a new TCP connections to the chat server tcpServer = new TcpClient(); tcpServer.Connect(ipAddr, 1986); //... //sending message from text box swSender.WriteLine(txtMessage.Text); swSender.Flush(); } }

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• Testing with Qt's QTestLib module

  - by ak

  Hi I started writing some tests with Qt's unit testing system. How do you usually organize the tests? It is one test class per one module class, or do you test the whole module with a single test class? Qt docs (or some podcast that I recently watched) suggested to follow the former strategy. I want to write tests for a module. The module provides only one class that is going to be used by the module user, but there is a lot of logic abstracted in other classes, which I would also like to test, besides testing the public class. The problem is that Qt's proposed way to run tests involved the QTEST_MAIN macro: QTEST_MAIN(TestClass) #include "test_class.moc" and eventually one test program is capable of testing just one test class. And it kinda sucks to create test projects for every single class in the module. Of course, one could take a look at the QTEST_MAIN macro, rewrite it, and run other test classes. But is there something, that works out of the box?

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• Rails created_at find condition...

  - by Dustin Brewer

  I'm attempting to sum daily purchase amounts for a given user. @dates is an array of 31 dates. I need the find condition to compare a date from the array to the created_at date of the purchases. What I'm doing below compares the exact DateTime for the create_at column. I need it to look at the day itself, not the DateTime. How can I write this so created_at is in between the date from the array? <% @dates.each do |date| %> <%= current_user.purchases.sum(:amount, :conditions = ["created_at = ?", date]) % <% end %

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• Posting an image and textual based data to a wcf service

  - by James Hay

  I have a requirement to write a web service that allows me to post an image to a server along with some additional information about that image. I'm completely new to developing web services (normally client side dev) so I'm a little stumped as to what I need to look into and try. How do you post binary data and plain text into a servic? What RequestFormat should I use? It looks like my options are xml or json. Can I use either of these? Bit of a waffly question but I just need some direction rather than a solution as I can't seem to find much online.

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• What web UI framework is most suitable for building dynamic pages / forms?

  - by waxwing

  Hello, We are at a stage where we are considering different Web UI frameworks (most likely component based ones such as GWT, JSF, Wicket, Vaadin, etc). One of the main use cases / constraints is that it must support generating dynamic pages. I.e., the page/form layout and components is stored in a database and is changeable at runtime, and from this pages are generated. We are also going to write static layouts, but that is not the main focus of this question. I thought maybe the user community here can share experiences of different frameworks in this context. Are there differences in ease of implementation and what is suitable?

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• strategy for observer pattern?

  - by fayer

  I want to use observer pattern for a logging system. We have got logObservers and logObservables. The class that will have to log something will implement iLogObservable and include these methods: private $logObservers = array(); public function addLogObserver($logObserver) { $this->logObservers[] = $logObserver; } public function removeLogObserver($logObserver) { $this->logObservers[] = $logObserver; } public function write($type, $message) { foreach($this->logObservers as $logObserver) { $logObserver->log($level, $message); ; } } Then I noticed, that a lot of classes that will use logging will have these methods and I have to copy paste. So isn't it better to have these methods in a class I call LogObservable or just Log and then use strategy (instantiate this class inside all classes that will have to log). When I change the methods in Log, all logObservables will be affected. However, I have not seen anyone use observer pattern with strategy pattern yet, but it seems to be very efficient and remove the duplications. What do you think?

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• How do you implement syntax highlighting?

  - by ML

  I am embarking on some learning and I want to write my own syntax highlighting for files in C++. Can anyone give me ideas on how to go about doing this? To me it seems that when a file is opened: It would need to be parsed and decided what type of source file it is. Trusting the extension might not be fool-proof A way to know what keywords/commands apply to what language A way to decide what color each keyword/command gets I want to do this on OS X, using C++ or Objective-C. Can anyone provide pointers on how I might get started with this?

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• Assigning a MVC Controller property from Asp.Net page

  - by JasonMHirst

  I don't know if I've understanding MVC correctly if my question makes no sense, but I'm trying to understand the following: I have some code on a controller that returns JSON data. The JSON data is populated based on a choice from a dropdown box on an Asp.Net page. I thought (incorrectly) that Session variables would be shared between the Asp.Net project and the MVC Project. What I'd like to do therefore (if this is possible), is to call a Sub on the MVC that sets a variable before the JSON query is run. I have the following: Sub SetCountryID(ByVal CountryID As Integer) Me.pCountrySelectedID = CountryID End Sub Which I can call by the following: Response.Write("http://localhost:7970/Home/SetCountryID/?CountryID=44") But this then results in a blank page - again obviouslly totally incorrect! Am I going about MVC the wrong way or do I still have a hell of a lot more learning to do? Is this even possible to do?

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• Silverlight data-driven application with NHibernate

  - by Tigraine

  Hi Guys, this is more of a subjective Question, but I'll ask it anyway. I'm about to develop a very data-centric application that has to run inside the browser. The frontend will be Silverlight, backed by a Fluent NHibernate service that runs server side. The problem here is: Wherever I look for data-driven silverlight app I wind up finding Silverlight RIA services examples, but nothing on how to build this without some ADO.NET stuff involved. I have little to no knowledge in WCF so far, but from the limited research I did it seems like WCF is pretty much the only way to let the client talk to the server. Are there any tutorials/best practices on how to write a Silverlight MVVM app that provides CRUD for a non-EF database? Suggestions would be very much appreciated. Thanks PS: I can't use .NET remoting. The backend has to run on IIS6 :(

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• How to use a CTabCtrl in a MFC dialog based application ?

  - by shan23

  I need to do something which i expected to be was simple - create a tab control which has 2 tabs, implying 2 modes of operation for my app. When user clicks on Tab1, he'll be presented with some buttons and textboxes, and when he clicks Tab2, some other input method. I noticed that there was a CTabCtrl class thats used in MFC to add tabs. However, once I added the tab ctrl using the UI designer, I couldn't specify how many tabs there'll be using property window. Searching on the net, I found some examples but all of them required you to derive from CtabCtrl , create 2 or more child dialogs etc and to write your own custom class. My question is, since I want to do something so basic, why couldn't I do it using the familiar Add Event handler/Add member variable wizard and then handle everything else inside my app's class ? Surely, the default CTabCtrl class can do something useful without needing to derive from it ?

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• Hanging Forms When I Drag And Move My Forms

  - by hosseinsinohe

  I Write a Windows Application By C Sharp. I Use a Picture in Background of my Form (MainForm) And I Use Many Picture in Buttons in This Form,And also I Use Some Panel And Label with Transparent Background Color. My Forms,Panels And Buttons has flicker. I solve this problem by a method in this thread. But Still when other Forms Start over this Form,my Forms hangs when I Drag and Move my Forms over this Form.How can I Solve this Problem to Move And Drags my Forms easily And Speed? Edit:: My Forms Load Data From Access 2007 DataBase file.I Use Datasets,DataGridViews And Other Components to Load And show Data in My Forms.

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• basic question with a dtd

  - by voodoomsr

  i need an element with the characteristics <!ELEMENT section ((comment*)|definition|(comment*))> but that is ambiguous, i get the next message in visual studio Multiple definition of element 'comment' causes the content model to become ambiguous. A content model must be formed such that during validation of an element information item sequence, the particle contained directly, indirectly or implicitly therein with which to attempt to validate each item in the sequence in turn can be uniquely determined without examining the content or attributes of that item, and without any information about the items in the remainder of the sequence. So how can i write correctly that? the correct structure is one definition surrounded by possibles comments elements.

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• Better performance to Query the DB or Cache small result sets?

  - by user169867

  Say I need to populate 4 or 5 dropdowns w/ items from a database. Each drop down will have < 15 items in it. These items almost never change. Now I could query the DB each time the page is accessed or I could grab the values from a custom class that would check to see if they already exist in ASP.Net's cache and only if they don't query the DB to update the cache. It's trivial for me to write but I'm unsure if the performace would be better or not. I think it would be (although not likely anything huge). What do you think?

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• Display array values from web service method

  - by chupinette

  Hello all! I'm new to web services and im actually trying to learn how to develop one in C#. I have the following method in my web service which actually displays an array of int when i test it. [WebMethod] public int[] FindID(string str1,string str2) { Customer obj = new Customer(); obj.FindMatch(str1,str2); return obj.customer_id; } Now in my web application in which i have a button, the code is as below: Dim obj As localhost.Service = New localhost.Service Dim str1 As String = Session("str1") Dim str2 As String = Session("str2") Response.Write(obj.FindID(str1, str2)) The problem is that only the first value from the array is being displayed. Can anyone please help me to solve this problem?

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• Single Large v/s Multiple Small MySQL tables for storing Options

  - by Prasad

  Hi there, I'm aware of several question on this forum relating to this. But I'm not talking about splitting tables for the same entity (like user for example) Suppose I have a huge options table that stores list options like Gender, Marital Status, and many more domain specific groups with same structure. I plan to capture in a OPTIONS table. Another simple option is to have the field set as ENUM, but there are disadvantages of that as well. http://www.brandonsavage.net/why-you-should-replace-enum-with-something-else/ OPTIONS Table: option_id <will be referred instead of the name> name value group Query: select .. from options where group = '15' - Since this table is expected to be multi-tenant, the no of rows could grow drastically. - I believe splitting the tables instead of finding by the group would be easier to write & faster to execute. - or perhaps partitioning by the group or tenant? Pl suggest. Thanks

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• How do I detect a loop in this linked list?

  - by jjujuma

  Say you have a linked list structure in Java. It's made up of Nodes: class Node { Node next; // some user data } and each Node points to the next node, except for the last Node, which has null for next. Say there is a possibility that the list can contain a loop - i.e. the final Node, instead of having a null, has a reference to one of the nodes in the list which came before it. What's the best way of writing boolean hasLoop(Node first) which would return true if the given Node is the first of a list with a loop, and false otherwise? How could you write so that it takes a finite amount of space and a reasonable amount of time?

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• Cucumber testing with rails on mongoid-gridfs

  - by Deepak Lamichhane

  I am getting this weird error while running cucumber test: ERROR Mongo::OperationFailure: Database command 'filemd5' failed: {"errmsg"="exception: best guess plan requested, but scan and order required: query: { files_id: ObjectId('4d1abab3a15c84139c00006e') } order: { files_id: 1, n: 1 } choices: { $natural: 1 } ", "code"=13284, "ok"=0.0} I have a list of similar scenarios, where first scenario passes but all the other following scenario fails. I searched for it and I found that there is problem with indexing. But, I am not sure about what query to write. Furthermore, I can add the query on the mongo of the development. I want to make sure that the indexing is done in test too. If anyone has any idea on this, feel free.

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• Solutions for redundant server and client code?

  - by Fragsworth

  In our system, the code which exists on the client side (in Flash and Javascript) mirrors the code that exists on the server side (e.g. in Python or PHP), normally with respect to the models, the methods available for those models, and the unit tests written for them. This becomes a problem in systems where you want to minimize data transfer (e.g. multiplayer games). I do not want to write the same code and unit tests redundantly for both the client and server, but I don't know of any standard solutions to deal with this. Basically, I want a language/compiler which can produce models and methods for three main languages: Actionscript, Javascript, and any server language. Does something like this exist?

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• Given two lines on a plane, how to find integer points closest to their intersection?

  - by Lukasz Lew

  I can't solve it: You are given 8 integers: A, B, C representing a line on a plane with equation A*x + B*y = C a, b, c representing another line x, y representing a point on a plane The two lines are not parallel therefore divide plane into 4 pieces. Point (x, y) lies inside of one these pieces. Problem: Write a fast algorithm that will find a point with integer coordinates in the same piece as (x,y) that is closest to the cross point of the two given lines. Note: This is not a homework, this is old Euler-type task that I have absolutely no idea how to approach. Update: You can assume that the 8 numbers on input are 32-bit signed integers. But you cannot assume that the solution will be 32 bit.

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• Iterate over a dict or list in Python

  - by Chris Dutrow

  Just wrote some nasty code that iterates over a dict or a list in Python. I have a feeling this was not the best way to go about it. The problem is that in order to iterate over a dict, this is the convention: for key in dict_object: dict_object[key] = 1 But modifying the object properties by key does not work if the same thing is done on a list: # Throws an error because the value of key is the property value, not # the list index: for key in list_object: list_object[key] = 1 The way I solved this problem was to write this nasty code: if isinstance(obj, dict): for key in obj: do_loop_contents(obj, key) elif isinstance(obj, list): for i in xrange(0, len(obj)): do_loop_contents(obj, i) def do_loop_contents(obj, key): obj[key] = 1 Is there a better way to do this? Thanks!

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• How do you use Java 1.6 Annotation Processing to perform compile time weaving?

  - by Steve

  I have created an annotation, applied it to a DTO and written a Java 1.6 style annotationProcessor. I can see how to have the annotationProcessor write a new source file, which isn't what I want to do, I cannot see or find out how to have it modify the existing class (ideally just modify the byte code). The modification is actually fairly trivial, all I want the processor to do is to insert a new getter and setter where the name comes from the value of the annotation being processed. My annotation processor looks like this; @SupportedSourceVersion(SourceVersion.RELEASE_6) @SupportedAnnotationTypes({ "com.kn.salog.annotation.AggregateField" }) public class SalogDTOAnnotationProcessor extends AbstractProcessor { @Override public boolean process(final Set<? extends TypeElement> annotations, final RoundEnvironment roundEnv) { //do some stuff } }

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• A little bit more complicated multiview App for Iphone

  - by Thomas Losert

  Hi, i'm new to iphone development. I spend several days by looking for how write muliview app for an Iphone OS. I found how to switch the diferent views without navigation hierarchy (in this article). It's great, but i want more complicated function. For example, i have three diferent views (view 1 - 3) and i can switch between them with technique from link 1. It works fine. My question is: How can i put UITabBarController on view 2, that shows own subviews (tabView 1 - 3) and how put UINavigationController on view 3, that shows own subviews (navView 1 - 2)? The reslut should look like that, one main view (view 1) with two buttons (for example), which switch me to "window" with UiTabBarController or UINavigationController. I found only tutorials, where UITabBarController was a first controller class, that shows directly from AppDelegate (something like default Xcode predefined scenarios). Thanks for your helpfull answer, or i will be crazy soon:).

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• Grouping items in php

  - by c0mrade

  Hello, I have a problem with sorting items in table in PHP. Here is what I want to achieve : Item Item Item Item Item Item Item Item Item Item Item Item Item Item Item How I mean to achieve this, well since I have a for each loop I can insert counter, and say after 5th item is listed write to another column, the thing is I'm not good with tables, I've tried something like : for(...) $counter++; if(($counter%5) == 0){ echo ""; } Not happening .. I hope you understood what I meant .. tnx

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